Research Interests

Special Topics

Experimental tests of Bell's Inequalities

While Eric Adelberger (UWash) was on sabbatical leave at CERN during
the academic year 1993-94, a discussion developed between us of the
published claims by theorist Emilio Santos (see references in our
paper below) that quantum mechanics may be interpreted within the
framework of so-called local hidden-variables models without
conflict with any known experiment. We found to be correct his
criticism of the use of Bell's inequalities to draw contrary
conclusions from experiments by Aspect and others, but were not
convinced that the experimental deficiencies were fundamental,
as Santos further conjectured. In a subsequent paper published in
PRL we presented a realistic (although extravagant) experiment
which defeats Santos' conjecture that Bell's inequalities are
in principle inaccessible to experimental tests.

In informal discussions with UConn physics major
Glen Maclachlan
about the Stern-Gerlach experiment, which provided experimental
confirmation of theoretical ideas about space quantisation and
intrinsic spin, we looked into the comparison between the behaviour
expected for classical and quantum spinors. In the process we
discovered some surprising subtleties in the problem which are
ignored in most textbook treatments of the subject. For more
information about this work, see
Glen's senior research project.

Non-sequential Double-Ionization of Atoms and Molecules

UConn graduate student Chunlei Guo (graduated 1998) studied for his
thesis project the ionization rates of atoms and molecules in the
intense field of a short-pulse high-power laser, under the guidance
of UConn professor George Gibson. His results showed a significant
excess in the double-ionization rate over what would be expected if
the two electrons were emitted in a sequence of two single-ionization
steps. This effect, called non-sequential double ionization (NSDI)
had been observed by others before. What Chunlei discovered was
that the NDSI rates for diatomic nitrogen and oxygen were different,
an effect which he hypothesized to be due to the different symmetries
of the valence electrons in the two molecules. Following discussions
of these ideas with Chunlei and George, we embarked on a project to
numerically simulate the two-electron system in the presence of the
ionizing field. With a little effort, the code developed with Glen
Maclachlan (see above) was revamped to describe the two-electron atom
with a time-varying background potential. Chunlei then used this
code to simulate both single and double-ionization. With it he was
able to reproduce the NDSI effect, and observed a significant dependence
in the NDSI rate on the symmetry of the initial two-electron state,
in agreement with his experimental observations.